The present invention relates to a carrier used for reinforcement of an elastomeric strip typically employed in sealing systems, such as for example, gripping and covering edge flanges surrounding an opening in a vehicle body. More particularly, the present invention relates to a carrier, which does not stretch when coated in an elastomeric extrusion process and which in turn does not shrink after being cut to length, installed, and used in the operating environment.
Carriers, such as wire carriers typically include a continuous wire weft formed into a serpentine frame having limbs interconnected by connecting regions at each end of the limbs, with a polymeric warp weft knitted, sewn, threaded, or otherwise disposed on the limbs.
Such a wire carrier is widely used, mainly as a reinforcing frame, which is encapsulated in a polymeric material especially in extruded products, such as weatherseals for motor vehicles. During the manufacture of the seals, the wire carrier is passed through an extrusion process and is thus subjected to stresses and elevated temperatures, which can cause the warp threads to stretch longitudinally. When the warp threads are processed with a tensile stress during extrusion, the resultant product may experience shrinkage after being finally sized and installed, which becomes a problem for the installer as well as the end customer.
In spite of these issues, the serpentine carrier provides substantial benefits. Specifically, the wire carrier exhibits an inherent flexibility about three axes, which in turn provides good handling characteristics of the finished product. In addition, the wire carrier is able to bear relatively high loading, particularly during the extrusion process. This is in contrast to many stamped as well as lanced and stretched metal carriers. In addition, the serpentine carrier has the benefit of withstanding greater flexing without exhibiting metal fatigue. Thus, there is a need to develop a stable serpentine carrier for extruded and molded polymeric products, which overcomes these problems.
The use of various materials for warp threads has reduced but not yet solved the problem of elongation. That is, even using warp threads made from materials having zero to very low elongation factors does not completely prevent a wire carrier from suffering from elongation and eventual shrinkage. For example, even if fiberglass threads, which have a very low elongation factor, were used as the warp threads in a wire carrier, the knotted junctions of the warp threads around the wire carrier substantially reduces the ability of the warp threads to reduce elongation of the warp threads and hence the wire carrier. While the short lengths of the warp thread between the knots may be free of elongation during extrusion, the knots themselves are apt to become tighter during extrusion and looser after processing, thereby changing the length of warp thread between the limbs. Thus, even employing warp threads with very low elongation factors may not effectively prevent carrier elongation and subsequent shrinkage.
Thus, there is a need to reduce final product shrinkage by reducing carrier elongation during pre-forming, extrusion, post-forming and cut to length. There is further a need to reduce the shrinkage that is realized in weatherseals in the short term after extruding, during secondary operations, and after extended time in the field. There is further a need to retain the spacing between the limbs of the carrier during extrusion processing, thereby preventing elongation. There is further a need for an inexpensive elongation prevention mechanism. There is a further need for such an elongation prevention mechanism, which is easy to incorporate into the manufacture of a serpentine carrier, such as a wire carrier, without requiring additional extrusion lines or substantially increasing material requirements.
The present invention provides a carrier with an elongation reducing member, which provides enhanced length stability in a resulting product, such as a weatherseal, while retaining the advantageous flexibility of a serpentine carrier. The present carrier includes an elongation reducing member, which is connected to a plurality of adjacent limbs in the carrier. Preferably, the elongation reducing member is flexible intermediate the adjacent limbs to retain the inherent flexibility of the carrier, and is sufficiently strong to preclude increased separation of the adjacent limbs.
The present invention further provides an elongation reducing member which is inexpensive, and can be employed without requiring retooling of existing extrusion dies or substantial increase material requirements.
In a first configuration of the present invention, a carrier for use in a weatherseal includes a filament such as a wire folded into a serpentine frame so as to have a plurality of limbs interconnected at alternate ends by connecting regions, the limbs generally extending transverse to a longitudinal axis of the carrier. The carrier has a width substantially defined by a length of one of the plurality of limbs. The filament has a given thickness, or diameter. The carrier also includes at least one elongation reducing member generally extending along the longitudinal axis of the carrier, wherein the elongation reducing member is connected to the plurality of limbs in a set down relationship. The set down relationship is a compression of a joint or crossing of the elongation reducing member and the serpentine frame such that the resulting thickness of the joint or crossing is less than the combined thickness of the elongation reducing member and the filament of the serpentine frame.
Optionally, the carrier can include a plurality of warp threads, such as polymeric warp threads, carried on and secured to the limbs by knitting, sewing, threading or otherwise secured to the serpentine frame to encompass a limb within a stitch of each knitted row of warp thread.
In one configuration, the elongation reducing member is a cable secured to a wire serpentine frame, such that the elongation reducing member extends substantially perpendicular to and is joined to the plurality of limbs of the serpentine frame. The resulting joint between each limb and the elongation reducing member defines a thickness that is less than a combined thickness of the wire and the elongation reducing member. In a preferred construction, the elongation reducing member is welded to the serpentine frame to have a set down greater than 20%. That is, at least 20% of the nominal thickness of the thinner one of the elongation reducing member or the frame is within the thickness of the thicker remaining one of the elongation reducing member and the frame. In a further preferred construction, the joint between the elongation reducing member and the filament of the serpentine frame has a thickness that is less than or substantially equal to the thickness of the filament. That is, the elongation reducing member has 100 percent set down with respect to the filament of the serpentine frame.
The carrier can include an elongation reducing member positioned in a central location along the plurality of limbs. In a preferred construction, the elongation reducing member is connected to the serpentine frame to define a neutral axis of the carrier. Alternatively, a first elongation reducing member may be positioned along a first longitudinal axis and a second elongation reducing member positioned along a second longitudinal axis. Alternate configurations are also within the scope of the invention.
A first method for manufacturing the carrier of the present invention, includes forming a filament, such as a wire, into a serpentine configuration having a plurality of limbs interconnected at alternate ends by connecting regions, feeding an elongation reducing member, such as a cable, and the serpentine frame into a welding station and welding the elongation reducing member to the serpentine frame. The method further includes welding the elongation reducing member to the serpentine frame to form a joint thickness that is less than the combined thickness of the filament and the elongation reducing member. A further configuration of the method includes welding the elongation reducing member to the serpentine frame to extend along the longitudinal axis of the carrier, such that the elongation reducing member is secured substantially perpendicular to the plurality of limbs. The method further includes selecting the welding station, the filament and the elongation reducing member to provide at least 20% set down, with a preferred set down of approximately 50% and a more preferred set down of approximately 100%. That is, the resulting joints have a thickness that is no greater than the thickness of the thicker one of the filament or the elongation reducing member.